Proteases are a family of enzymes that catalyze the hydrolysis of peptide bonds and are known to exist in a wide variety of microorganisms, animals and plants. They are commonly used in various fields for laundry detergents, automatic dishwashing detergents, contact lens detergents, bath additives, keratolytic cosmetics, food modifiers (e.g. breadmaking, meat tenderization and fish processing), clarifying agents for beer, leather tanning agents, gelatin removing agents for photographic films, digestion promoting preparations and anti-inflammatory preparations, for example.
Unfortunately, proteases hydrolyze themselves and other proteins to remarkably decrease the activities of their own and of the other proteins over time.
Some approaches to inhibiting the hydrolysis of proteases themselves and other proteins focus on protease inhibitors that inhibit protease activity. As examples of protease inhibitors, Streptomyces subtilisin inhibitor (SSI) from Streptomyces species (Non Patent Literature 1) and chymotrypsin inhibitor 2 from barley (Non Patent Literature 2) are mentioned.
Unfortunately, because of their too strong inhibitory activity, most of known naturally occurring protease inhibitors, when used in protease solutions, do not allow the solutions to be reactivated by dilution prior to use.